cryptoe commented on code in PR #13952:
URL: https://github.com/apache/druid/pull/13952#discussion_r1170874096
##########
processing/src/main/java/org/apache/druid/query/scan/ScanQueryQueryToolChest.java:
##########
@@ -217,77 +218,106 @@ public Optional<Sequence<FrameSignaturePair>>
resultsAsFrames(
)
{
final AtomicLong memoryLimitAccumulator = memoryLimitBytes != null ? new
AtomicLong(memoryLimitBytes) : null;
- Yielder<ScanResultValue> yielder = Yielders.each(resultSequence);
- RowSignature prevSignature = null;
- List<Cursor> unwrittenCursors = null;
- List<FrameSignaturePair> frameSignaturePairs = new ArrayList<>();
- while (!yielder.isDone()) {
- ScanResultValue scanResultValue = yielder.get();
- final List rows = (List) scanResultValue.getEvents();
- final Function<?, Object[]> mapper = getResultFormatMapper(query);
- final Iterable<Object[]> formattedRows = Iterables.transform(rows,
(Function) mapper);
+ Iterable<FrameSignaturePair> iterable = () -> new
Iterator<FrameSignaturePair>()
+ {
+ ScanResultValue nextScanResultValue = null;
+ Yielder<ScanResultValue> yielder = Yielders.each(resultSequence);
+ boolean started = false;
+
+ @Override
+ public boolean hasNext()
+ {
+ return !yielder.isDone() || nextScanResultValue != null;
Review Comment:
This looks to me a impl of peeking iterator.
`com.google.common.collect.PeekingIterator`
##########
processing/src/main/java/org/apache/druid/query/scan/ScanQueryQueryToolChest.java:
##########
@@ -217,77 +218,106 @@ public Optional<Sequence<FrameSignaturePair>>
resultsAsFrames(
)
{
final AtomicLong memoryLimitAccumulator = memoryLimitBytes != null ? new
AtomicLong(memoryLimitBytes) : null;
- Yielder<ScanResultValue> yielder = Yielders.each(resultSequence);
- RowSignature prevSignature = null;
- List<Cursor> unwrittenCursors = null;
- List<FrameSignaturePair> frameSignaturePairs = new ArrayList<>();
- while (!yielder.isDone()) {
- ScanResultValue scanResultValue = yielder.get();
- final List rows = (List) scanResultValue.getEvents();
- final Function<?, Object[]> mapper = getResultFormatMapper(query);
- final Iterable<Object[]> formattedRows = Iterables.transform(rows,
(Function) mapper);
+ Iterable<FrameSignaturePair> iterable = () -> new
Iterator<FrameSignaturePair>()
+ {
+ ScanResultValue nextScanResultValue = null;
+ Yielder<ScanResultValue> yielder = Yielders.each(resultSequence);
+ boolean started = false;
+
+ @Override
+ public boolean hasNext()
+ {
+ return !yielder.isDone() || nextScanResultValue != null;
+ }
- if (prevSignature == null ||
!prevSignature.equals(scanResultValue.getRowSignature())) {
-
- if (unwrittenCursors != null && prevSignature != null) {
- FrameWriterFactory frameWriterFactory =
FrameWriters.makeFrameWriterFactory(
- FrameType.ROW_BASED,
- new
SingleMemoryAllocatorFactory(HeapMemoryAllocator.unlimited()),
- prevSignature,
- new ArrayList<>(),
- true
- );
- Cursor concatCursor = new ConcatCursor(unwrittenCursors);
- Frame frame = FrameCursorUtils.cursorToFrame(
- concatCursor,
- frameWriterFactory,
- memoryLimitAccumulator != null ? memoryLimitAccumulator.get() :
null
- );
- if (memoryLimitAccumulator != null) {
- memoryLimitAccumulator.getAndAdd(-frame.numBytes());
+ @Override
+ public FrameSignaturePair next()
+ {
+ if (nextScanResultValue == null) {
+ if (!started) {
+ nextScanResultValue = yielder.get();
+ yielder = yielder.next(null);
+ started = true;
+ return next();
+ } else {
+ throw new NoSuchElementException();
+ }
+ }
+ List<ScanResultValue> batch = new ArrayList<>();
+ RowSignature signature = nextScanResultValue.getRowSignature();
+ batch.add(nextScanResultValue);
+ boolean updatedNextScanResultValue = false;
+ while (!yielder.isDone()) {
+ ScanResultValue potentiallyBatchableScanResultValue = yielder.get();
+ if (signature != null &&
signature.equals(potentiallyBatchableScanResultValue.getRowSignature())) {
+ batch.add(potentiallyBatchableScanResultValue);
+ yielder = yielder.next(null);
+ } else {
+ nextScanResultValue = potentiallyBatchableScanResultValue;
+ updatedNextScanResultValue = true;
+ yielder = yielder.next(null);
+ break;
}
- frameSignaturePairs.add(new FrameSignaturePair(frame,
prevSignature));
}
- unwrittenCursors = new ArrayList<>();
- unwrittenCursors.add(IterableRowsCursorHelper.getCursorFromIterable(
- formattedRows,
- scanResultValue.getRowSignature()
- ));
+ // We are done iterating over the elements, and next call to hasNext()
should return false
+ if (yielder.isDone() && !updatedNextScanResultValue) {
+ nextScanResultValue = null;
+ }
- } else {
- unwrittenCursors.add(IterableRowsCursorHelper.getCursorFromIterable(
- formattedRows,
- scanResultValue.getRowSignature()
- ));
- }
+ FrameSignaturePair retVal = convertScanResultValuesToFrame(batch,
signature, query, memoryLimitAccumulator);
- prevSignature = scanResultValue.getRowSignature();
- yielder = yielder.next(null);
- }
+ if (memoryLimitAccumulator != null) {
Review Comment:
Nit: Please push memoryLimitAccumulator inside convertScanResultValuesToFrame
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